# Question #6901d

Feb 23, 2018

$4 i \sqrt{7}$

#### Explanation:

To simplify the expression $2 \sqrt{- 28}$, you have to use the term $i$.

$i = \sqrt{- 1}$ which is the imaginary unit.

You can rearrange the equation into:

$2 \sqrt{- 1 \cdot 28}$
$2 \sqrt{- 1} \sqrt{28}$
$2 i \sqrt{28}$

Now to simplify inside the radical, you need to factor out a perfect square from 28. The only one that comes to mind is four. Make 28 into $4 \cdot 7$.

$2 i \sqrt{4 \cdot 7}$
$2 i \sqrt{4} \sqrt{7}$

The square root of 4 becomes 2. Hence:

$2 i \cdot 2 \sqrt{7}$

$4 i \sqrt{7}$